A type of power generation device for a mobile body has been proposed that generates power based on a relative flow of external fluid when the mobile body travels. Patent Document 1 discloses such a device, which includes a wind turbine arranged under the hood of a vehicle. The wind turbine is rotated by a flow of outside air during traveling and generates power. Patent Document 2 discloses a configuration including power generation devices of an electromagnetic induction type arranged in the supporting portions at both ends of a rear spoiler. In this configuration, the energy of vertical vibrations of the rear spoiler caused by a flow of outside air during traveling is converted into electrical energy.